Midkine stimulates Wilms' tumor cell proliferation via its signaling receptor

Midkine, but not pleiotrophin, is mitogenic to human Wilms' tumor cells (G401 line) in dose-dependent and time-dependent fashion. Midkine specifically binds to high affinity (Kd = 0.15 +/- 0.02 nM, 210 kDa) and low affinity receptors (Kd = 0.65 +/- 0.07 nM, 75 kDa) on G401 cell surface, that has been confirmed by cross-linking and competition experiments. In addition, midkine stimulates a tyrosine phosphorylation of several proteins with molecular weight about 110-115 kDa, 130-140 kDa and 210 kDa. These data allow us to suggest that a key point in stimulation of G401 cell proliferation is interaction of midkine to its signaling receptor.